The present disclosure relates to systems and methods for percutaneous implantation of a prosthetic heart valve. More particularly, it relates to systems and methods for transcatheter implantation of a stented prosthetic heart valve.
Diseased or otherwise deficient heart valves can be repaired or replaced with an implanted prosthetic heart valve. Conventionally, heart valve replacement surgery is an open-heart procedure conducted under general anesthesia, during which the heart is stopped and blood flow is controlled by a heart-lung bypass machine. Traditional open surgery inflicts significant patient trauma and discomfort, and exposes the patient to a number of potential risks, such as infection, stroke, renal failure, and adverse effects associated with the use of the heart-lung bypass machine, for example.
Due to the drawbacks of open-heart surgical procedures, there has been an increased interest in minimally invasive and percutaneous replacement of cardiac valves. With percutaneous transcatheter (or transluminal) techniques, a valve prosthesis is compacted for delivery in a catheter-based delivery device and then advanced, for example, through an opening in the femoral artery and through the descending aorta to the heart, where the prosthesis is then deployed in the annulus of the valve to be repaired (e.g., the aortic valve annulus). Although transcatheter techniques have attained widespread acceptance with respect to the delivery of conventional stents to restore vessel patency, only mixed results have been realized with percutaneous delivery of the more complex prosthetic heart valve.
Various types and configurations of prosthetic heart valves are available for percutaneous valve replacement procedures, and continue to be refined. The actual shape and configuration of any particular transcatheter prosthetic heart valve is dependent to some extent upon the native shape and size of the valve being repaired (i.e., mitral valve, tricuspid valve, aortic valve, or pulmonary valve). In general, prosthetic heart valve designs attempt to replicate the functions of the valve being replaced and thus will include valve leaflet-like structures. With a bioprostheses construction, the replacement valve may include a valved vein segment that is mounted in some manner within an expandable stent frame to make a valved stent (or “stented prosthetic heart valve”). Oftentimes, the stent frame of the valved stent is made of a self-expanding material and construction. The corresponding percutaneous delivery/implantation devices generally assume one of two forms. In many instances, the delivery device is constructed such that the valved stent is crimped down to a desired size and held in that compressed arrangement within an outer delivery sheath, for example. Retracting the sheath from the valved stent allows the stent to self-expand to a larger diameter, such as when the valved stent is in a desired position within a patient. In other percutaneous implantation devices, the valved stent can be initially provided in an expanded or uncrimped condition, then crimped or compressed on a balloon portion of a catheter until it is as close to the diameter of the catheter as possible. The so-loaded balloon catheter is slidably disposed within an outer delivery sheath. Once delivered to the implantation site, the prosthesis is removed from the delivery sheath and the balloon is inflated to deploy the prosthesis. With either of these types of percutaneous stented prosthetic valve delivery devices, conventional sewing of the prosthesis to the patient's native tissue is typically not necessary.
In addition to the delivery device itself, typical transcatheter heart valve implantation techniques entail the use of a separate introducer device to establish a portal to the patient's vasculature (e.g., femoral artery) and through which the prosthetic heart valve-loaded delivery device is inserted. The introducer device generally includes a relatively short sheath and a valve structure. By inserting the prosthesis-containing delivery sheath through the introducer valve and sheath, a low-friction hemostasis seal is created around the outer surface of the delivery sheath. While highly desirable, friction between the introducer device and the delivery sheath can be problematic, leading to unexpected movement of the prosthesis prior to release from the delivery device.
In particular, with a self-expanding stented prosthetic heart valve, the outer delivery catheter or sheath is retracted from over the prosthesis, thereby permitting the stented valve to self-expand and release from the delivery device. Friction between the introducer device and the delivery sheath has a tendency to resist necessary proximal movement of the delivery sheath. Because the retraction force is initiated at a handle of the delivery device, this resistance is transferred to the handle. As a result, unless the clinician (and/or an assistant) carefully holds both the handle and the introducer device in a fixed position relative to one another throughout the deployment operation, the handle has a tendency to draw forward. This movement, in turn, is transferred onto the delivery device component (e.g., an internal shaft) otherwise coupled to the loaded prosthetic heart valve, potentially moving the internal component (including the loaded prosthetic heart valve) forward or distally within the patient. While unintended, even a slight displacement from the expected deployment location of the prosthesis relative to the native annulus can lead to severe complications as the prosthesis must intimately lodge and seal against the native annulus for the implantation to be successful. If the deployed prosthesis is incorrectly positioned relative to the native annulus, the deployed stented valve may leak or even dislodge from the implantation site.
For example, FIG. 1A illustrates, in simplified form, an introducer device 10 establishing a portal to a patient's vasculature 12, and through which a prosthetic heart valve-loaded delivery shaft 14 (the tip of which is visible in FIG. 1A) has been inserted. As shown, the delivery shaft 14 has been manipulated to locate the loaded prosthetic heart valve 16 (referenced generally) in a desired position relative to an aortic valve 18. An outer delivery sheath 20 contains the prosthesis 16. Thus, in the state of FIG. 1A, the prosthetic heart valve 16 is properly positioned for deployment from the delivery shaft 14 upon proximal retraction of the delivery sheath 20 relative thereto, with a spacing S being established between a distal end of the delivery device's handle 22 and the introducer device 10. As shown in FIG. 1B, an actuator 24 of the handle 22 is moved by the clinician in an attempt to proximally pull or retract the delivery sheath 20 and release the prosthesis 16. Frictional interface between the delivery sheath 20 and the introducer device 10 may resist proximal movement of the delivery sheath 20 (conventionally, the introducer device 10 is held stationary). As a result, the handle 22 is instead pulled forward toward the introducer device 10 (reflected in FIG. 1B by a decrease in the spacing S). In effect, the handle 22 is being advanced over the delivery sheath 20 rather than the delivery sheath 20 being retracted into the handle 22. Forward movement of the handle 22 is, in turn, directed onto the delivery shaft 14, causing the delivery shaft 14 to distally advance (represented by the arrow B in FIG. 1B) and displace the deploying prosthetic heart valve 16 from the desired valve implantation site 18. While it may be possible to provide an additional isolation layer between the introducer device 10 and the delivery sheath 20, distinct constraints render implementation of an additional layer highly problematic. For example, the tortuous nature of the patient's vasculature necessitates that the delivery device have as low a profile as possible, thereby limiting an available size of the additional layer. Conversely, any additional layers must account for and facilitate necessary retraction of the delivery sheath 20 during a deployment operation.
In light of the above, although there have been advances in percutaneous valve replacement techniques and devices, there is a continued desired to provide different delivery systems for delivering cardiac replacement valves, and in particular self-expanding, stented prosthetic heart valves to an implantation site in a minimally invasive and/or percutaneous manner.